Experimental Design Practice Handout	

Complete this set of practice questions to prepare for the Experimental Design Quiz.  You are allowed to use this worksheet to take the quiz.  You may see the same or very similar questions on the quiz.

Identifying Variables:
For each of the following experiments, identify the independent and dependent variables.  Here is an example to start you off.		 	 		
	 		 		 	 	 		
Example: An experiment was done to determine if a plant would grow faster if it were fertilized.
Independent (Manipulating) Variable: The amount of fertilizer 
Dependent (Responding) Variable: How fast the plant grows
											
1.	An experiment was done to determine if the time it takes to run a kilometer is related to the amount of exercise a person gets.
Independent Variable: 				Dependent Variable: 

2.	An experiment was done to determine if the rate at which an egg cooked depended on the temperature of water in which it was boiled.
Independent Variable: 				Dependent Variable:  

3.	An investigation was done to see if keeping the lights on for different amounts of time each day affected the number of eggs chickens laid.
Independent Variable: 				Dependent Variable: 

4.	An experiment was done to determine if the temperature of water in a lake varied at different depths.
Independent Variable: 				Dependent Variable: 

5.	An experiment was done to determine if grass will grow taller if it is watered weekly than grass that is not watered.
Independent Variable: 				Dependent Variable: 

Experimental Design: 
Read through each of the following experiments.  Draw a picture, if necessary, to understand the experimental setup.  Answer the questions that follow.

Pig Digestion Experiment
A sample of digestive juice was removed from the stomach of a pig. The juice was placed in a test tube along with some grains of wheat. A second test tube was set up containing an equal number of wheat grains, with distilled water rather than digestive juice. The test tubes were kept for 8 hours at 40 degrees C. After 8 hours the grains inside the digestive juice had broken into tiny particles. The grains of wheat, in the water, were wet but otherwise unchanged.

What is the control group? 
What is the experimental group?
What is the independent variable?
What is the dependent variable?
Name a controlled variable or constant.
Was quantitative or qualitative data collected?

Caffeine for Fruit Flies Experiment
An experiment was designed to investigate the effect of caffeine on the rate of the heartbeat of fruit flies. Two populations of fruit flies were grown in a lab. Both populations were raised drinking the same type of water and the same type of food. Both populations were exposed to the same amount of light and regulated temperature at 20 degrees Celsius. The fruit flies’ heartbeats were then monitored at two hour intervals. The fruit flies of population one were given caffeine five minutes before their heartbeat was checked. The fruit flies of population two were not given any caffeine.

What is the control group? 
What is the experimental group?
What is the independent variable?
What is the dependent variable?
Name a controlled variable or constant.
Was quantitative or qualitative data collected?

A Look Back at Redi’s Experiment.  Complete the following passage with the vocabulary words below.

Redi designed a controlled experiment to disprove the theory of spontaneous generation.  He put meat in two jars.  One jar was left uncovered and the other was covered with gauze.  The jar left open for flies to enter was the _____________ group.  The jar manipulated with the gauze covering to keep flies out was the _______________ group.  

The presence or absence of the gauze is the __________________ variable, or the factor that was different between the two groups. The ______________ variable was what was measured - whether or not maggots appeared on the meat.  Redi kept all of the other factors in the experiment constant, or the same.  These are also called _________________ variables.

controlled       experimental       independent        dependent       control